What’s Vulnerable › Vulnerabilities

CVE-2025-66490: Traefik doesn't Prevent Path Normalization Bypass in Router + Middleware Rules

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2025-12-09 · updated 2026-10-14
• Weakness: CWE-436

Description

Traefik is an HTTP reverse proxy and load balancer. For versions prior to 2.11.32 and 2.11.31 through 3.6.2, requests using PathPrefix, Path or PathRegex matchers can bypass path normalization. When Traefik uses path-based routing, requests containing URL-encoded restricted characters (/, \, Null, ;, ?, #) can bypass the middleware chain and reach unintended backends. For example, a request to http://mydomain.example.com/admin%2F could reach service-a without triggering my-security-middleware, bypassing security controls for the /admin/ path. This issue is fixed in versions 2.11.32 and 3.6.3.

Affected products

• Traefik: before 2.11.32; from 3.0.0 before 3.6.3 — fixed in 2.11.32, 3.6.3

How to fix

Upgrade to a fixed version: Traefik 2.11.32, 3.6.3. Check the vendor advisory for mitigations.

References

• https://github.com/traefik/traefik/releases/tag/v2.11.32
• https://github.com/traefik/traefik/releases/tag/v3.6.4
• https://github.com/traefik/traefik/security/advisories/GHSA-gm3x-23wp-hc2c
• https://github.com/traefik/traefik/security/advisories/GHSA-gm3x-23wp-hc2c

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